I'm one of those people who change it every few days, if not every day.
Only BORING LOSER people don't change it.
Damn, Luke Skywalker has been my desktop for months. This means I must be boring....
I've had Austin Springs at work for something nearing a year.
At home, I have a unique BogGoblin.co.uk wallpaper which has been on my PC for about 18 months. This, of course, not only means I'm boring but means that I'm a narcissistic egomaniac.